Apparatus for crushing and sorting solid particles



R. A. REICHEL Jan. 28, v1969 APPARATUS FOR CRUSHING AND SORTING SOLIDPARTICLES Sheet 012 Filed July 25, 1966 ONTROL CIRCUI INVENTOR. RICHARDA. REICHEL ATTORNEYS Jan. 28, 1-969 7 R. A. REICHEL 8 APPARATUS FORCRUSHING AND SORTING SOLID PARTICLES Filed July 25, 1966 Sheet 2 of 2 33J I I5 SENSING 03 0 46 47 COIL A.

45 MIXER, DET

44 v 'TG I I FI J GI 52 42 37 I 7 v H /4| \JUUI R"" C2 Ql INVENTOR.RICHARD A. REICHEL ATTORNEYS United States Patent 7 Claims Int. Cl. B02c13/00 ABSTRACT OF THE DISCLOSURE Apparatus for sorting minerals with ametallic content above a given value from minerals whose metalliccontent is below that given value. Sample minerals to be sorted are fedfrom a conveyor to the central region of a rotating table that impelsthe minerals under centrifugal force through a plurality of radiallyaligned passages. Minerals with metallic content above the given valueare automatically detected by electronic sensors which cause doorsmounted at the exit ends of the passages to swing downwardly and deflectthe minerals into an inner annular receiving chamber. In the case ofother minerals, the deflecting doors remain in retracted positionsenabling the minerals to pass into an outer receiving chamberconcentrically aligned with the inner one. Oversized minerals arecrushed by a rotatable inertial plate positioned above the table.

This invention relates generally to sorting apparatus and moreparticularly to a novel mineral sorting apparatus for separating into atleast two groups, pieces of mineral differing from each other inaccordance with a given characteristic.

Many mineral sorting systems are presently known in the art. Basically,these systems function to automatically separate minerals into variouscategories according to their size, specific gravity, or other physicalor magnetic characteristic.

In those cases in which it is desired to separate pieces of mineralwhich have no significant physical or magnetic properties different fromthe pieces of waste rock much more complex equipment is required. Someof the problems involved include the provision of suitable means forenabling a piece-by-piece sensing of the mineral and the separating ofthe same in accordance with the particular characteristic for which thestructure is designed. The piece-by-piece sensing of the pieces ofmineral itself raises various problems which include, among others, thedesign of a system wherein a large volume of 'mineral pieces can besorted in a relatively short period of time without requiring anenormously bulky apparatus, the problem of assuring that the pieces ofmineral to be analyzed do not exceed a certain size which might jam thesensing mechanism, and the provision of a sensing means sufficientlyresponsive to the desired characteristic to minimize errors in sorting.Of these problems, that dealing with a system enabling a piece-by-pieceanalysis to take place and yet handle a large volume of minerals in arelatively short period of time without undue bulk and expense is one ofthe most important.

With the foregoing considerations in mind, it is a primray object of thepresent invention to provide a novel mineral sorting apparatus in whichthe above problems are resolved to a considerable extent.

3,424,388 Patented Jan. 28, 1969 "ice More particularly, it is an objectto provide a novel mineral sorting apparatus capable of effecting apiece-bypiece analysis of minerals and separating the same into at leasttwo groups in an extremely rapid manner and without undue bulk.

Another important object is to provide a mineral sorting apparatusincorporating unique means for limiting the size of pieces of mineral tobe analyzed so that the risk of stopping or jamming of the apparatus isminimized.

Still another important object is to provide, in combination with asorting apparatus meeting the foregoing objects, a unique electronicsensing system which is sufficiently sensitive as to enable separationof minerals in accord with their metallic content.

A more general object along the lines of the preceding object is toprovide a mineral sorting apparatus so designed that different types ofsensing equipment may be substituted to enable separation of pieces ofmineral in accordance with characteristics diflerent from their metalliccontent, such as their color or other optical, electrical, radiation,chemical, or physical properties.

Other objects of this invention are to provide a mineral sortingapparatus which may be easily monitored while in operation, and which isrelatively economical to construct, compact in size, and extremelyrugged in design and construction to the end that it will provide longand trouble-free service.

Briefly, these and many other objects and advantages of this inventionare attained by providing a basic rotary means mounted for rotationabout a vertical axis and defining a plurality of passages havingentrance ends adjacent to the central portion of the rotary means andexit ends adjacent to the periphery of the rotary means.

Raw mineral pieces are passed into the central portion of the rotarymeans such that minerals received in this portion are caused to travelalong the passages individually by centrifugal force upon rotation ofthe rotary means. By providing several such passages on a singlerotating structure, several pieces of mineral may be analyzedsimultaneously.

At the exit ends of each of the passages, there is provided a deflectingmeans and a suitable control means including a sensing means foractuating the deflecting means. When apiece of mineral, which has acharacteristic different from other pieces of mineral in accordance withthe desired separation or grouping of the mineral pieces, passes thesensing means, the sensing means actuates the deflecting means todeflect the particular piece of mineral in question as it is thrown fromthe exit opening of the passage into a suitable receiving chamber.

There is thus provided a separation of pieces of mineral having a givencharatceristic from the remaining pieces of mineral.

In the preferred construction of the sorting apparatus, there isprovided an outer shell and inner shell structure defining an outerannular receiving chamber which surrounds the peripheral exit ends ofthe various passages in a position to receive pieces of mineral that arenot deflected. The inner shell serves to define an inner chamber whichwill in turn receive pieces of mineral that are deflected. The annularshell structures are generally coaxial with the vertical axis ofrotation of the rotary means resulting in an overall compactconfiguration for the entire sorting apparatus.

A better understanding of the invention as well as further uniqueadvantages and features will be had by now referring to a preferredembodiment thereof as illustrated in the accompanying drawings, inwhich:

FIGURE 1 is a perspective view, partly broken away, of the mineralsorting apparatus of this invention shown in conjunction with a conveyorbelt for passing minerals to the apparatus;

FIGURE 2 is a partially exploded, broken away, perspective view of thestructure illustrated in FIGURE 1;

FIGURE 3 is a fragmentary plan view looking generally in the directionof the arrows 33 of FIGURE 2;

FIGURE 4 is an enlarged fragmentary perspective view of a portion of thestructure illustrated in FIGURE 3 looking in the direction of the arrow4;

FIGURE 5 is a greatly enlarged fragmentary view partly in cross sectionof the sorting apparatus;

FIGURE 6 is a schematic circuit diagram of the sensing and actuatingmeans employed in the sorting system; and

FIGURE 7 shows an automatic tuning circuit.

Referring first to FIGURE 1, there is indicated generally by the numeral10 the mineral sorting apparatus wherein there is provided an entranceopening indicated by the arrow 11 for receiving pieces of mineral 12from a conveyor 13. As shown, the pieces of mineral are dropped onto anupper conical wall 14 in an upper outer shell structure 15 of theapparatus.

The lower portion of the apparatus is comprised of an outer lower shell16 including outlet tubular structures 17 and 18 for passing separatedpieces of mineral into suitable containers such as indicated at 19 and20.

In the particular embodiment to be described, the pieces of mineral 12are separated into two groups in accordance with a given characteristicsuch, for example, as their metallic content. However, it is to beunderstood that any other type of given characteristic may becontrolling such as physical, optical, or chemical properties of themineral pieces in question.

Referring now to FIGURE 2, further details of the structure will bedescribed. As shown, the 'funnel opening 14 merges into a cylindricaltubular portion 21 upon which is rotata'bly mounted an inertia plate 22having downwardly directed projections 23 and 24, the purpose for whichwill become clearer as the description proceeds. The lower portion ofthe structure includes an inner shell 25 cooperating with the outershell 16 to define an outer annular receiving chamber 26. This annularreceiving chamber 26 communicates with the tubular structure 17 asshown. The inner shell 25 also defines an inner receiving chamber 27which communicates with the tubular outlet structure 18, as shown.

The outer and inner receiving chambers surround a rotary means in theform of a rotary table 28 on the surface of which there are defined aplurality of passages preferably extending generally radially in anarcuate manner as indicated at 29. The rotary table 28 is mounted forrotation on a shaft 30.

It will be noted from the plan view of FIGURE 3 that the variouspassages 29 are all identical and are designed such that when the rotarystructure is rotated in the direction of the arrows, pieces of mineralreceived in the central portion of the rotary structure will be causedto travel radially outwardly along the passages by centrifugal force.

Referring now particularly to FIGURE 4, one of the passages 29 will bedescribed in detail. Since these passages are all the same, descriptionof one will suifice for all. As shown, the passage includes an entranceand 31 adjacent the central portion of the rotary structure and an exitopening 32 adjacent the periphery of the rotary structure. At this exitportion of the passage, there is provided a deflecting means preferablyin the form of an overhead door 33 hinged to the upper end edge of theexit end 32 as shown. Door 33 is normally held in an horizontaloutwardly extending position as by a biasing spring 34. The position ofthe door 33, as shown, constitutes a first position.

The door 33 is arranged to be moved to a second position by a solenoidactuated structure 35 in response to a suitable signal derived from asensing means including a sensing coil 36 constituting part of a controlcircuit 37. It will be noted that the sensing coil 36 is positionedadjacent the exit end 32 of the passage in such a manner that pieces ofmineral passing down the passage 29 will pass close to the coilstructure 36.

The foregoing design is such that when the solenoid structure 35 isenergized, the door 33 will be swung downwardly towards a partiallyclosed position in which its inside surface will constitute a deflectingsurface to deflect any pieces of mineral passing down the passage 29 tothe inner receiving chamber 27. When the door is in its first oroutwardly extending position illustrated in FIGURE 4, any pieces ofmaterial thrown from the exit end 32 of the passage will pass over theinner receiving chamber 27 and be received in the outer annularreceiving chamber 26.

Referring now to FIGURE 5, the foregoing as well as other features ofthe invention will be better understood.

As shown in FIGURE 5, the inertia plate 22 referred to in FIGURE 2 ismounted as by bearings 38 for free rotational movement about the tubularportion 21 of the entrance opening 14 in the upper shell 15. It will benoted that the projections 23 and 24, which may be in the form of rigidmetallic bars welded to the underside of the inertia plate 22, terminatea given distance above the floor of the rotary table 28. This givendistance is slightly less than the exit opening dimensions for thevarious passages such that over sized minerals received in the centralportion of the rotary means and thrown outwardly towards the entranceend of the passages as by centrifugal force will be engaged by theprojections 23 and 24. This engagement causes the inertia plate 22 torotate but because of its inertia, the mineral piece is crumbled orcrushed, and any other pieces engaged by the projections 23 and 24 aresimilarly crushed or broken in size such that they will readily passdown the various passages. It is to be understood that the bearings forthe inertia plate permit vertical as well as rotational movement so thatdamage to the apparatus is prevented.

With respect to the foregoing, an important feature of the inertia plateis that it will simply rotate with the rotating passages in the eventthat a non-crushable object such as a large piece of steel is fed to theapparatus. Continuous rotation of the inertia plate can be sensed toautomatically stop the feed to the machine and thus prevent furtherjamming. Suitable brushes indicated generally by the number 40 pass froma stationary power supply 41 to the slip rings 39 to regulated powersupplies 42 to provide energy for these particular circuits. Electricalsignals which indicate the operational condition of each sensing meansalso are transmitted through the slip rings. In this respect, it will beevident that the passages individually include control circuits, sensingmeans, and solenoid actuated deflecting means all carried with therotary table 28 along with the regulated power supplies 42 so that thesame rotate with the rotary structure.

With the foregoing description of FIGURES 1-5 in mind, the overallgeneral operation of the sorting apparatus will now be described.Initially, mineral pieces to be sorted are passed in the direction ofthe arrow 11 are illustrated in FIGURES 15 by any suitable means such asthe conveyor 13. The motor M in FIGURE 5 is started so that the rotarytable 28 is rotated at a fairly high speed. The inertia plate 22 willnot rotate unless the downwardly projecting portions 23 and 24 encounteroversized pieces of mineral.

As the pieces of mineral are received in the central portion of thetable, they will be caused to travel by centrifugal force outwardlythrough the entrance openings of the various radially extending passages29. Oversized pieces of mineral will strike the projections 23 and 24and tend to become wedged or crushed thereby causing partial rotation ofthe inertia plate 22. The downwardly projecting portions 23 and 24 willthus sweep over the upper surface of the central portion of the rotarystructure and as long as any mineral pieces are larger than of a size topass down the passages, they will engage the inertia plate and becrushed.

The dimensioning of the passages relative to the inertia plateprojections is such that the mineral pieces will pass one at a timethroughthe various passages out towards the exit openings. As the piecestravel through the passages they become separated from each other asthey gain velocity thus allowing the sensing and separation ofindividual pieces. Normally, the deflecting means such as the door 33shown in FIGURE 5 remain in their first positions so that the mineralswill be thrown to the outer annular receiving chamber 26, as illustratedat the left of FIGURE 5. However, if any one mineral piece has ametallic content, as one example of a given characteristic, exceeding agiven amount, in passing the sensing coil 36, there will be developed asignal employed to actuate the solenoid 35 and move the deflecting meanssuch as the means 33 to its second position or partially closedposition. As an example, the deflecting means for the passage way on theright side of FIGURE 5 is shown in the partially closed or secondposition. The mineral providing the actuating signal will then strikethe inside sloping surface of the deflecting means and thus be guided ordeflected into the inner annular chamber 27 With reference to FIGURES land 2, it will be noted that the mineral pieces that are not deflectedbut are received in the annular outer receiving chamber pass through thetubular structure 17 to the container 19 whereas the mineral pieceshaving a metallic content exceeding a given amount which are deflectedto pass into the inner chamber 27 pass to the container 20. The ore ormineral pieces are thus separated into first and second groups dependingon the particular given characteristic controlling the sorting.

The manner in which the sensing means determines whether or not aparticular piece of mineral has a metallic content greater than a givenamount will now be understood by reference to FIGURE 6. In FIGURE 6, thecontrol circuit for each of the sensing means and deflecting meansassociated with the exit end of each passage designated generally by thenumeral 37 is illustrated. Each of these control circuits are identical.Thus, referring first to the upper lefthand corner of FIGURE 6, thesensing coil 36 is schematically shown and constitutes part of a firstoscillator A designated generally by the numeral 43. This oscillatorwill oscillate at a given frequency but this frequency will be variedupon passing of a mineral piece with metallic content close to thesensing coil 36 as a consequence of a changing in the tuningcharacteristics of the coil 36.

Cooperating with the oscillator 43 is a fixed coil 44 constituting partof a fixed tuned oscillator B designated by the numeral 45. Thefrequency of the oscillator 45 is fixed at a frequency valuecorresponding within a given limit to the frequency of the oscillator Ain the absence of any metallic bearing mineral. The outputs from theoscillators A and B pass to a mixer 46 and detector 47 which willprovide an output signal constituting a function of the beat frequencyof the frequencies of oscillator A and oscillator B. This beat frequencywill be determined by the frequency difference between the twooscillators, and in the absence of any minerals having any metalliccontent, this frequency difference will be within the given limit asdescribed.

The output of the detector 47 passes through a coupling condenser C1 tothe base of an amplifying transistor Q1. The output from the transistorQ1 is taken from its collector terminal and is in the form of a seriesof constant amplitude pulses 48, the frequency of which corresponds tothe beat frequency. Capacitance C2 is alternately charged and dischargedand the resulting current through the diodes D1 and D2 is directlyproportional to the beat frequency. The junction point 49 connects to afurther capacitor C3 shunted by the diodes D1 and D2, respectively,oriented in opposite directions as shown. This circuit arrangementincluding resistance R6 results in a given voltage V1 at the junctionpoint 49.

From the junction point 49, the output signal passes through a couplingnetwork R2 and condenser C4 to the base of a second transistor Q2. Theoutput of the second transistor Q2 at a junction point 50 is again takenfrom the juncture of the collector of the transistor and collectorresistance R3 wherein a voltage V2 is developed. The voltage V2 passesthrough a resistance R4 to the base of a third transistor Q3. The outputof this transistor is shown at V3 and is taken from a junction point 51of the collector resistance R5 and passes to a suitable switch forproviding energy to the solenoid 35. When the voltage V3 at the junctionpoint 51 exceeds a given value, the solenoid 35 will be operated.

The circuit is completed by a voltage supply line 52 powered from thepower supply line 41 through the slip ring depicted schematically at 39and regulated power supply 42. This power supply provides B+ power forthe transistors as through the collector resistances R1, R3 and R5, thevarious emitters of the transistors all connecting to ground line 53.

In operation, the number of the pulses 48 per unit time is reflected bythe voltage V1 at the junction point 39. Thus, the resistor R6 andassociated diodes D1 and D2 all designated generally by the numeral 54serve to provide a voltage V1 which is proportional to the currentflowing through the condenser C2, which is turn is a function of thenumber of the pulses 48 per unit time. Condensers C3 and C4 andresistance R2 serve to filter the pulses into a fairly even voltage atthe base of Q2. This portion of the circuit thus functions generally asa counting circuit and will provide a voltage V1 at the junction point49 which is a direct function of the number of pulses 48 per unit time.

In the absence of any metallic bearing minerals passing the sensing coil36, the beat frequency is sufiiciently low that the voltage V1 will holdthe transistor Q2 in a partially on condition. As a consequence, thevoltage V2 at the junction point 50 will be between the power supplyvoltage and ground potential and transistor Q3 will be held in aconducting condition so that the voltage V3 at the junction point 51 atthe collector of the transistor Q3 will be low as a consequence ofvoltage drop across R5. In fact, there will be reflected essentially ashort circuit so that V3 will be substantially at ground potential andthe solenoid will remain unactuated so that the various doors willremain in their first positions.

If now a piece of mineral having a metallic content greater than a givenamount passes the sensing coil 36, the oscillator A will becomesufficiently detuned with respect to the oscillator B that the beatfrequency will increase beyond a given frequency resulting in a numberof pulses 48 per unit time greater than that number appearing in theabsence of any mineral having a metallic content. The voltage VI at thejunction point 49 will thus increase sufliciently to turn on andsaturate the transistor Q2 resulting in the voltage V2 at the junctionpoint 50 dropping because of the resistance R3. Dropping of the voltageV2 will then turn off the transistor Q3 as this change in voltage isreflected at the base of the transistor Q3, resulting in the voltage V3at the junction 51 increasing substantially to the power supply voltageon line 52. When the voltage V3 reaches this value, it will operate asuitable switch to energize the solenoid 35 and thus move the deflectingdoor 33 to its partially closed or second position and deflect themineral to the inner chamber 27.

After the mineral piece has passed, the beat frequency resumes itsnormal lower value so that the solenoid is de-energized and the doorimmediately opened again by the spring 34 preparatory to the analysis ofthe next succeeding piece of mineral.

To assure proper operation of the electronic portion of the circuit overlong periods of time, there is preferably included an automatic tuningmeans 55 for the fixed oscillator B. This automatic tuning meansessentially detects the voltage V2 at the junction point 50 and willretune the oscillator 45 so as to maintain a fixed frequency differencewith respect to the oscillator 43 in the absence of any metallic contentbearing mineral pieces.

Thus, with reference to FIGURES 6 and 7, at the referred to fixedfrequency difference or beat frequency, Q2 is held in a partiallyconducting condition as described. The value of R6 is chosen to providea voltage V1 approximately half way between the saturation and cut-offbase voltage for Q2. If the beat frequency changes, V1 changes and thischange is amplified by Q2 causing a large change in V2. The voltage V4in FIGURE 7 gradually follows the changes of V2. The diode D3 has acapacitance which varies with the reverse voltage across it. Thus D3functions as a voltage variable capacitor and since the frequency ofoscillator B depends in part on the value of this variable capacitance,the beat frequency will change when V4 changes.

In operation, as the beat frequency changes and V2 changes, theresulting change in V4 will cause the frequency of oscillator B to shiftin such a direction as to cause the beat frequency to return to itsoriginal value. Since rapid changes in V2 are not followed by V4,because of R7 and C5, this circut compensates for long drifts withoutreducing sensitivity.

In order to provide a continuous indication of the operation of thecircuits, each circuit includes a tap ofI' lead for the voltage V1passing through one of the slip rings 39 through a stationary meter 56to ground. Observation of this meter will thus permit monitoring of thestate of the circuit in question.

From the foregoing description, it will be evident that the presentinvention has provided a novel mineral sorting apparatus. While thesensing portion of the apparatus has been described in conjunction withseparating minerals in accordance with their metallic content, it shouldbe understood that any type of sensing means may be employed foroperating the deflecting means. In this respect, sensing means may beprovided which will generate a signal to operate the solenoid inresponse to differences in optical characteristics of pieces of mineralssuch as their color or, for that matter, in response to other physical,electrical, chemical, or optical characteristics.

Further, while the deflecting means has been illustrated as includingsmall solenoid operated doors, other deflecting means might be used suchas jets of air operable by the solenoids for small, light pieces ofmineral.

The mineral sorting apparatus is therefore not to be thought of aslimited to the particular example set forth merely for illustrativepurposes.

What is claimed is:

1. A mineral sorting apparatus for dividing pieces of mineral into atleast two groups differing from each other in accord with a given amountof metallic content in said pieces of mineral, comprising, incombination: a rotary means including a plurality of radially outwardlyextending passage means along which pieces of mineral are caused totravel by centrifugal force when received in the central portion of saidrotary means and said rotary means is rotated; deflecting means at theouter end portions of each of said passage means; and electronic sensingmeans in each of said passage means coupled to actuate associateddeflecting means in response to a piece of mineral having said givenmetallic content passing said sensing means, whereby pieces of mineralhaving said given metallic content are deflected upon leaving saidpassage means and thereby separated from the rest of said pieces ofmineral.

2. A mineral sorting apparatus for dividing pieces of mineral into atleast two groups differing from each other in accord .with a givencharacteristic, comprising, in combination: a horizontally disposedrotary means mounted for rotation about a vertical axis, said rotarymeans defining a plurality of horizontal passages having entrance endsadjacent the central portion of said rotary means and exit ends adjacentthe periphery of said rotary means such that minerals received in saidcentral portion are caused to travel along said passages by centrifugalforce upon rotation of said rotary means; an outer shell structure; aninner shell structure defining with said outer shell structure an outerannular receiving chamber surrounding said rotary means, said innershell defining one wall of an inner annular receiving chamber having anentrance whose inner wall is defined by said rotary means periphery;deflecting means at the exit ends of each of said passages movablebetween a first position in which minerals are free to pass from theexit ends of said passages and be received in said outer annularreceiving chamber and a second position in which minerals are deflectedto pass into said inner annular receiving chamber; and control meansincluding sensing means at the exit ends of each of said passages andresponsive to the passing of pieces of mineral having said givencharacteristic to move said deflecting means from said first to saidsecond position whereby minerals having said given characteristic arereceived in said inner chamber and all other minerals are received insaid outer chamber.

,3. An apparatus according to claim, 2, including an inertial platemeans mounted for rotation about said vertical axis in axially spacedrelationship to the floor of said passages and central portion of saidrotary means and including mineral engaging projecting means terminatinga given distance above said floor whereby any minerals of dimensionsgreater than said given distance are engaged and crushed by saidprojecting means upon rotation of said rotary means so that onlyminerals less than a given size pass along said passages.

4. An apparatus according to claim 2, in which said deflecting means foreach of said passages includes a solenoid actuated overhead door, hingedalong the upper end edge of the exit end of the associated passage forswinging movement from a generally horizontally extending directiondefining said first position to a partially closed condition in whichthe inner side of said door defines a downwardly sloping deflectingsurface defining said second position.

5. An apparatus according to claim 4, in which each deflecting means andcontrol means for actuating its associated door are carried by saidrotary means; a vertical shaft mounting said rotary means; a motor fordriving said shaft; and slip ring means carried by said shaft forpassing electrical energy to each control means.

6. An apparatus acording to claim 2, in which said given characteristicconstitutes a metallic content in said mineral, said control meanscomprising a first oscillator having an oscillating coil constitutingsaid sensing means, passing of a piece of mineral having a metalliccontent changing the frequency of oscillation of said coil; a secondoscillator having a frequency corresponding within a given limit to thefrequency of said first oscillator in the absence of any mineral havinga metallic content; mixer, detector, and amplifying means connected tosaid first and second oscillators for providing a beat frequency signalarising from the difference in the frequencies of oscillation of saidfirst and second oscillators; and means responsive to said beatfrequency signal for actuating said deflecting means when the frequencyof said beat frequency signal exceeds a given frequency.

7. An apparatus according to claim 6, including automatic tuning meansresponsive to said beat frequency signal for maintaining the frequencyof oscillation of said second oscillator within said given limit of thefrequency of said first oscillator in the absence of any mineralshavinga metallic content passing by said oscillating coil.

References Cited UNITED STATES PATENTS 653,792 7/ 1900' Dasconaguerre209-420 1,358,375 11/1920 Koch 209120 X 2,045,769 6/ 1936 Geficken 20911.8- X

3,117,080 1/ 1964 Krestin 209-1 3,283,899 11/1966 Vedvik 2091 X FOREIGNPATENTS 929,046 6/ 1955 Germany.

FRANK W. LUTTER, Primary Examiner.

US. Cl. X.R.

